There are generally used various kinds of cards such as bank cards being used for the automatic withdrawal of cash from banks, credit cards being used in the credit sale transactions, or ID cards being used for the identification of individuals who enter normally restricted zones or buildings or rooms.
By way of such kinds of cards, there are usually made use of magnetic cards being provided with a magnetic registration field in the form of a magnetic stripe. In these magnetic registration fields, there are stored card registration numbers. However, the use of such cards is stopped for various reasons such as missing or stolen cards or bad payment on the card account. Taking case of the credit cards, in stores or restaurants where the cards are used, validity checking has been made so far by comparing a list of invalid registration numbers against the card registration number visually displayed on the magnetic card being used, so that not only is time and labor required but also some invalid numbers may be left unnoticed while on the other hand this method is sometimes capable of giving customers a somewhat unpleasant feeling. In addition to these circumstances, even though a reference check for the registration number is in some cases made to the credit company by taking advantage of the terminal equipment being connected to a host computer, employment of this practice is not popular because of place and time restrictions and considerable expense, and as a result the card registration number being recorded magnetically is not made use of with efficiency.